Amazon said the acquisition will help it offer more and better digital comic books and graphic novels.

Founded in 2007, comiXology offers digital comic books from more than 75 publishers, including industry giants Marvel and DC, plus independent creators. ComiXology's headquarters will remain in New York.

Shares of Amazon.com Inc. fell $14.79, or 4.5 percent, to $317.amid a broader market sell-off. The Dow Jones Industrial Average ended the day down 267 points or 1.6 percent.